Jasna,
 
I haven't noticed an answer to your question, so here goes another
uninformed opinion from the man on the street.  Hydrogen peroxide will
react with just about anything - even by itself as it is unstable with
an extra oxygen atom and this is what makes it work.  That foaming
coating plus a bleach bath would most likely leave a shell dull, clean
but dull -- kind of like some people I used to know.  Anyway, just spray
your slit shell with silicone or carefully wipe it with mineral oil and
all of the colors should come right back.  I prefer the silicone because
it is easier and I have a really dangerous tendency to drop the shell
when I am wiping on or wiping off mineral oil.  Age certainly hasn't
improved my shell handling abilities - but I am a bit wiser and try to
stay away from situations where I know my chances of seeing a shell jump
out of my greasy hands is just too high to risk.  The silicone just gets
sprayed on and evaporates in a few hours.
 
Tom Eichhorst in New Mexico, USA
 
Oh, there is one time I always use mineral oil.  Sometimes you will get
a shell with small fractures/cracks in the glossy coating (any part of a
cowry, the inside lip of a strombus, etc.)  I have never tried silicone
on these but I know that mineral oil works wonders.  As you wipe it on
the cracks seem to almost completely disappear and stay that way.
Silicone might work as well or better - I just have never tried.  As for
the folks who still want to use WD-40.  I tried it on an abalone and
found it sparked the shell up for a few weeks but them seemed to
evaporate or whatever and the shell was dull again.  A coating of
silicone solved this and it seems to really last at least as well as
mineral oil.
 
Jasna Peternel wrote:
 
> Few days ago I decided to clean my P.westralis.There were organic
> remains inside and the shell was little smelly.So I injected some
> hydrogen peroxide inside but it didn't work.
> I remowed the peroxide from the shell(but didn't splash inside with
> water).Then I put entire shell in a 30% chlorine bleach
> solution.
> A rapid reaction (between peroxide and bleach ???) which lasted about 5
> seconds happend.After 20 minutes I took the shell out from the bleach.
> It became dull,faded,colorless.
>
> What happened?
>
> Milan